A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor section and the fan section. The turbine section is connected to the fan section through a shaft.
During periods of elevated or maximum load on conventional gas turbine engines, force from the turbine section pulls the shaft in an aft direction. Generally, this force is at least partially counteracted by the fan section pulling the shaft in a forward direction and bearing assemblies along the shaft.
However, gas turbine engines with a gear train, such as an epicyclic gear train, between the fan section and the turbine section that allows the shaft to rotate faster than the fan section, separate the axial loads carried by the fan section and the turbine section. This separation of axial loads occurs because the epicyclic gear train carries torsional loads and not axial loads. Therefore, the fan section no longer counteracts forces pulling the turbine section in the aft direction. Thus, the bearing assemblies along the shaft must support the increased load which results in increased bearing size or decreased bearing life.